
Only you discover if your username and password have been compromised.In order to make this computation more efficient, Chrome sends a 3-byte SHA256 hash prefix of your username to reduce the scale of the data joined from 4 billion records down to 250 records, while still ensuring your username remains anonymous. This allows us to compare your encrypted username and password with all of the encrypted breached usernames and passwords, without revealing your username and password, or revealing any information about any other users’ usernames and passwords. In order to determine if your username and password appears in any breach, we use a technique called private set intersection with blinding that involves multiple layers of encryption.

No one, including Google, is able to derive your username or password from this encrypted copy.
